THE FRESH-WATEH MUSSEL. 



93 



reaches all around the front of the mantle to the place 

 where the two halves are joined behind. This opening 

 is called the ventral siphon (Fig. 91). It is the edge 

 of this lower opening that you lift up to enter one of 

 the chambers of the mussel. He has but two rooms ; 

 and this one that you enter by the large lower opening, 

 or ventral siphon, is the larger of the two. * This is 

 the room in which the mussel keeps his foot, which is 

 the biggest part of him (Fig. 92). He must belong to 

 the yellow-skinned race, for his foot is very yellow, and 

 such an odd shape ! more like a ploughshare than a foot, 

 though the foot of the cockle, another brother of the 

 mussel, looks like the foot of a fat baby. The toe of 

 the foot is turned toward the anterior or front end of 

 the shell (Fig. 92), and it bends downward a little tow- 

 ard the lower ventral border, the shape of your foot 

 when you pull your heel back against your ankle. 

 The foot contains elastic muscle in its walls, and, when 

 our little friend gets tired of staying in one place, and 

 wants a change of air or food, he uses these muscles to 

 push his foot through his mantle by the ventral 

 siphon (Fig. 91), the large lower opening, and then 

 out between the edges of the shell. Then he curves 

 his foot and hooks it on to something, while he pulls 

 the rest of his establishment after him ; but, for the 

 most part, the mussel is not a traveler. He bores or 



